In the discussion of the background that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art.
Various different forms of equipment and machinery can be employed for mining and excavation operations. Typically, it is the type of mining or excavation taking place, and the type of earth being mined or excavated, that dictates the type of equipment and machinery that is appropriate. Commonly, equipment and machinery for such purposes include a cutting pick mounted on a rotating element either directly or via a block or via a block and sleeve assembly. In operation, the cutting picks rotate with the rotating element to impact against and to dislodge or fragment earth from the face being contacted. Cutting picks employed for the above purpose generally have a hard cemented tungsten carbide tip, which is fixed, usually by brazing, to a head of the cutting pick, and a steel shank. Cutting picks of this kind are disclosed in various publications, such as U.S. Pat. No. 6,113,195.
Wear is of concern in such operations. Wear occurs from both relative rotation of elements of the block and sleeve and from face-to-face impact of elements with each other. For example, a cutting pick is generally designed to rotate about its longitudinal axis to more evenly wear the tip, to self-sharpen, and to prolong its service life. At the same time, the cutting pick is forced backwards during operation and has a rearward facing surface of a shoulder that impacts a forward face of the mounting, such as the forward face of the block.
Cutting picks directly mounted in the bore of the block can wear on the block. To minimize adverse wear of the block, a sleeve can be interposed between the cutting pick and the block as a sacrificial part for the wear that occurs as the cutting pick rotates and the faces contact. Although the sacrificial sleeve provides some protection from wear for the block, it is still advantageous to further minimize wear. Therefore, to minimize the wear between the sleeve and block assembly, rotation and/or impact motion between the sleeve and the block should be minimized.